I'm working on a deferred rendering engine and trying to figure out how to determine what area of the screen is affected by a light, so I can alter the rendering quad to only cover that area of the screen when creating the light map, instead of drawing the entire screen once per light. Hope that makes sense.

So I'm using Viewport.Project on the lights bounding frustum....but Project returns a Vector3. Am I doing this right, and how do I get a 2d quad from the Vector3 returned by Project?